TUESDAY, May 29 (HealthDay News) -- Preventive antiretroviral treatment appears to be an effective way to help protect high-risk people against HIV infection, a new study suggests.

HIV, the virus that causes AIDS, can be transmitted through unprotected sex and contaminated needles.

Immediate treatment after HIV exposure can be successful in preventing HIV infection, previous research has found. More recently, several large randomized, controlled trials -- the gold standard of medical research, in which people are randomly assigned to treatment or no treatment -- have shown that giving antiretroviral drugs before people are exposed may also prevent infection.

For the new report, published May 28 in the CMAJ (Canadian Medical Association Journal), researchers reviewed studies published between January 1990 and April 2012 and found that preventive antiretroviral treatment could reduce the risk of HIV infection in high-risk groups such as gay men, intravenous drug users, and women in areas with high rates of HIV.

For example, one recent study that included 900 women from a region with a high rate of HIV found that applying a topical vaginal microbicide 12 hours before and after sex led to a 39 percent reduction in HIV infection rates.

"All pre-exposure prophylaxis [prevention] interventions should be considered one part of a more comprehensive plan for preventing the spread of HIV infection, including standard counseling on safer sexual practices and condom use, testing for and treating other sexually transmitted infections and, in select circumstances, male circumcision and needle exchange programs," Dr. Isaac Bogoch of Harvard Medical School and Massachusetts General Hospital in Boston, and colleagues wrote.

While pre-exposure treatment is promising, there are a number of unanswered questions, such as which groups would benefit most, and the possibility of the development of drug resistance, the researchers noted.

More information

The U.S. Centers for Disease Control and Prevention has more about HIV transmission.